[CMake] Adding Cmake version in online documentation

[Alexander Neundorf]

On Wednesday 09 November 2016 09:22:24 Nils Gladitz wrote:
...
> You said you are not forcing your users to upgrade by setting a policy
> to OLD.
> Which implied that not setting the policy to OLD would force your users
> to upgrade ... which it doesn't.
> 
> >> In fact all that setting it to OLD does is suppress the warning.
> > 
> > It's better than emitting zillion of warnings to the output, right?
> > You can suppress one type and fix another, set TODOs, etc.
> 
> Policy warnings are intended to encourage you to switch to new
> behaviours since the old ones are deprecated.
> In actively maintained projects they are not meant to be suppressed.


I heard that argumentation several times, and still don't agree.

"actively maintained" doesn't automatically mean to always require the newest 
versions of everything, see the mail from Albrecht Schlosser (FLTK) or how 
CMake requirements were handled during the KDE4 era.

To make the software buildable on as many as possible systems, it helps to not 
to require new versions of any needed tools or libraries.

So, Albrecht can absolutely actively maintain FLTK, and at the same time 
decide to require a relatively old cmake version (Ok, 2.6 is ancient).

As long as he doesn't plan to update the required version for cmake, I would 
suppress all policy warnings about new behaviour.
Is it guaranteed that changing the code so that the warning, which appeared 
e.g. in cmake 3.4, is fixed, still works correctly with the old, required 
version of cmake ?
I think no.

Once there is a plan to upgrade the cmake version, the warnings become useful, 
but IMO not before.

Alex